1. Field of the Invention
Aspects of the present invention relate to an electrolyte for a rechargeable lithium battery and a rechargeable lithium battery including the same. More particularly, the present invention relates to an electrolyte for a rechargeable lithium battery having excellent storage stability at a high temperature, and a rechargeable lithium battery including the same.
2. Description of the Related Art
A lithium rechargeable battery has recently drawn attention as a power source of a small portable electronic device. Such a secondary battery uses an organic electrolyte solution to achieve a discharge voltage twice as high as a conventional battery using an alkali aqueous solution, and accordingly has a high energy density. For a positive active materials of a rechargeable lithium battery, lithium-transition element composite oxides being capable of intercalating lithium, such as LiCoO2, LiMn2O4, LiNiO2, LiNi1-xCoxO2 (0<x<1), LiMnO2, etc., have been researched. As for a negative active material of a rechargeable lithium battery, various carbon-based materials, such as artificial and natural graphite, and hard carbon, have been used, which may all intercalate and deintercalate lithium ions. Positive and negative electrodes of a rechargeable lithium battery may be unstable depending on a charge state at a temperature of 25° C. or more and may thereby induce decomposition of a salt of the electrolyte, an organic solvent, and the positive and negative active materials. This decomposition causes serious deterioration of battery stability and safety. In order to counter such decomposition, an electrolyte including 0.001 to 0.1 mol/L of an organic compound having at least two cyano groups has been suggested. However, sufficient stability and safety have not been realized. High-capacity batteries are required to meet the demands of customers, while high-level stability and safety are also required, and it is difficult to satisfy both requirements.